Concrete laying machine



July-28, 1936.v H. M. HADLEY CONCRETE LAYING MACHINE Filed March 3l, 1935 E MENEN Patented July 28, 1936 UNITED STATES.

TENT

CONCRETE LAYING MACHINE Homer M. Hadley, Seattle, Wash. Application Marchc 31, 1933, Serial No. 663,698

37 Claims. (Cl. 94-46) This invention relates to an apparatus and method for laying concrete, and while the invention may be employed in thelaying of concrete iioors of large area, it is intended to be zespecially useful when applied in the laying of concrete pavements.

When concrete is being laid to form a floor, pavement or roadway, it is necessary to tamp the upper side of the laid concrete to condense it, and to bring it to the desired surface. This operation is usually accomplishedby hand and requires the employment of many hands on the job. It has been attempted to lay concrete pavements or roadways by advancing -a hopper along the pavement or roadbed, so that the concrete is laid in a transverse strip as wide as the pavement or roadway. However, it is necessary to provide joints in concrete pavements or roadways, and the machinery used heretofore o; for this purpose, does not provide means for readily forming these joints; neither does it afford means for adequately compacting and condensing concrete having a low water content, the use of which is highly desirable.

. The forming of joints considerably increases the cost of building concrete pavements, and an improved and more economical means of making them, is desired.

The general object of this invention is to provide improved apparatus and an improved method for laying concrete and compacting it, avoiding the necessity for the usual hand tamping operations, and enablingl the water and cement content to be reduced.

i5, A further object is to provide an improved ap;

paratus and improved method for laying a concrete pavement or roadway which will facilitate the forming of expansion joints at suitable intervals, and also planes of weakness at which the 40 cross-section of the concrete is reduced.

Another object of the invention is to provide a method and 4apparatus which will facilitate the forming of contraction joints or planes of weakness in a concrete pavement while being 45 laid, and enabling a reduction in the number of regular expansion joints, these planes of weakness, or secondary joints being so formed that they will tend to form transverse fractures in the concrete, that develop after the concrete 50 has stood for some time, and in this way cooperating with the expansion joints to provide for contraction, expansion, and/or settling of the pavement.

The general purpose of this is to induce the formation of spaced rectilinear fractures intermediate between the usual joints, and thereby prevent the formation of irregular cracks which otherwise tend to form irregularly in all concrete roadways or pavements, as the .concrete ages.

One of the objects of the invention is to pro- 5 vide means for vibrating the vertical end or face of the strip of concrete being laid by the machine. Y

A further object is to provide for the placing of reinforcing in the concrete. Further objects of the invention will appear hereinafter.

The invention consists in the method described hereinafter, and resides also in the novel parts and combination of parts to be described herel5 inafter, all of which contribute to produce an eiflcient concrete laying machine.

A preferred embodiment of the invention is described in the following specification, while the broad scope of the invention is pointed out in the appended claims.

In the drawing:

Figure 1 is a longitudinal section taken through my apparatus, representing the same in the act of laying a concrete strip, and illustrating a connection to a tractor drawbar broken away.

Figure 2 is a longitudinal section illustrating a strip of thelaid concrete after the machine has deposited it and passed on. In other words, Figure 2 may be considered as an extension at the 30 right end of Figure 1.

Figure 3 is a fragmentary view, and illustrates an enlargement of parts illustrated in Figure 1 at the end of the concrete strip that is being laid, and particularly illustrating details of the construction which facilitate the introduction of joint fillers for forming the regular expansion joints in the concrete, that is to say, joints that extend through the full depth of the laid concrete.

Figure 4 is a cross-section taken about on the line 4 4 of Figure 1, passing through the laid concrete and showing a portion of its cross-section. This view, however, omits parts of the .apparatus beyond the point where the section is taken.

Figure 5 is a side elevation broken away and showing a portion of a comb which I employ for impressing the laid concrete to form transverse weakened planes between the main joints.

Before proceeding to a more detailed description of my apparatus and method, it should be stated that in accordance with my method, l lay the concrete in a continuous strip, at a substantially uniform speed, preferably through the agency of a gravity feed from a hopper which is pulled along preferably by a tractor. At regular intervals I form transverse through joints that extend through the full depth of the concrete, and between these joints I impress the upper face of the laid concrete at intermediate points to form transverse planes of weakness. 'I'his impressing is preferably accomplished by a transverse bar or comb which is provided with a plurality of downwardly projecting spurs that form deep cavities or pockets in the laid concrete, and the under side of this bar is preferably provided with a rib that forms a relatively shallow groove in the upper face of the concrete connecting the pockets formed by the spurs. 'I'hese pockets should be numerous enough and deep enough to form weakened transverse planes, that is, so that the cross-section at these pockets, will be suiliciently weakened to insure that when a crack forms, it will form in this weakened plane. The forming of a contraction joint or weakened plane in the concrete in this way, is advantageous for the reason that when the crack forms, it will develop an irregular fracture which keys the material together across the crack; this tends to prevent vertical and lateral shifting of onesection at the crack with respect to the adjacent section. Provision is also made for producing a llongitudinal groove, or grooves for forming dummy joints.

My method eliminates the need for premolded joint llers in the transverse weakened plane joints, and avoids the necessity for finishing and rounding the edges of joints as in the present practice; and produces a pavement having a superior and smoother surface.

The comb may be operated by hand, and as a separate tool, but is preferably mounted on the apparatus and arranged to be operated by power.

In addition to a vibrating head located at the forward end of the concrete strip as it is laid, I also provide a cover plate or vibrating plate which rests on the upper side of the laid concrete, and which is given more or less of a vibratory vertical movement as the hopper advances. This movement may, if desired, be a substantial upand-down movement, but preferably consists of slight vertical vibrations at a high speed imparted to the cover plate by suitable mechanical means. The apparatus also preferably includes a plurality of cover plates or follower plates which are articulated to the cover plate, and winch are drawnalong with the hopper as it advances, thereby producing a smooth upper surface for the concrete, and tending to eliminate slight irregularities of surface.

ated periodically while the apparatus is stationary, to impress the concrete, thereby forming planes of weakness.

Referring more particularly to the parts, and especially to Figure 1, I indicates a hopper frame in which a hopper 2 is mounted for carrying concrete 3. This concrete would be supplied from a mixer by any desired and suitable-means. Any desired feeding arrangement may be provided for feeding the concrete from the hopper onto the roadbed or subgrade on which the concrete strip 5 is being laid. The width of the hopper determines the width of the strip laid. I prefer to provide a gravity outlet in the form of a contracted throat 6 for the concrete at the bottom of the hopper.

The hopper may be supported at its ends on temporary wooden side rails or sills 1, on which At therear end of the apparatus I prefer to mount the comb, which is operon the subgrade 4. 'Ihe traction frame, or 10 vibrator frame 9 is provided to carry an upright, but not necessarily substantially vertical header plate I I, which is preferably provided with means for vibrating the forward end of the concrete strip as the concrete is being placed. This header plate lies in a plane substantially perpendicular to the nished surface of the concrete. The apparatus for actuating this header plate is preferably located under a hinged cover plate I2 which projects over the header plate, and which may be 20 raised when necessary to give accessto the mechanism for oscillating or vibrating this plate II. Any suitable means may be employed for actuating this header plate I I. For this purpose I prefer to provide a transverse shaft I3 mounted in the 25 frame 9 under the cover plate, and provided with a plurality of eccentrics I4 which reciprocate corresponding eccentric rods I5, the ends of which are all riveted to the header plate II, and supported and guided in a frame member 9a. The 30 eccentricity of the eccentrics I4 may be suited to the particular conditions, and to the character of the vibrating action desired. Under some circumstances, the eccentricity can be made very slight, or nil, and eccentric weights may be em- $5.

ployed on the shaft I3, or connected with the eccentrics to produce vibrations in the header plate II in a horizontal direction. It will be noted that the tractor advances the hopper 2 in the direction of the arrow indicated in Figure 1, so that the header plate II is located forward of the delivery outlet 6. The header plate I I should not drag on the subgrade, as that would tend to dampen its vibrations.

To the rear of the delivery outlet 6 with respect to the direction of advance, I provide a cover plate I6 which rests on the laid concrete. This cover plate is mounted in any suitable manner for enabling it to be given a vibrating action in a vertical direction. For this purpose I prefer to support it at its forward end on pivot pms Il secured to the hopper frame, and in addition to this, I support the plate on a plurality of links I 8 which are pivotally attached at their upper ends to a transverse shaft I9 mounted on the hopper frame. This shaft is located adjacent the inclined guide plate or bottom plate of the hopper, and is provided at a plurality of points along its length, with eccentric weights 20 which cause vertical vibrations as the shaft I3 60v revolves. Any suitable driving means may be provided for rotating the shafts I3 and I 9. For this purpose I may provide the forward end of the traction frame with a stub shaft 2I carrying a pulley 22 driven by a b`elt 23 from the tractor, 55

and this stub shaft 2| drives a belt 24 or endless chain that drives the shaft I3. The shaft I3 is provided at one end with bevel gearing 25 for driving an extensible shaft 26 that extends up in an inclined direction to the shaft I9, which it drives through suitable bevel gearing 21.

The hopper frame is constructed so that it can be drawn forward over the rearend of the traction frame or vibrator frame, for a purpose that will presently appear.

I provide means for disconnecting the traction frame or vibrator frame 8 from the hopper frame, to enable the header plate I I to be moved slightly away from the laid concrete, so as to form a gap back of the header plate, into which a joint filler.3|J can be introduced. For this purpose I may provide the hopper frame with hooks such as hook 3| carrying traction chains 32 attached at their forward ends to hooks 33 on the traction frame. After inserting the filler 30, the hopper should be immediately advanced over the rear end of frame 9 until the filler lies under the rear edge of the hopper outlet 6. Then the frame 9 should be slowly advanced while operating the header plate Il to lay concrete and pack the same against the-forward side of the ller as indicated at 29. (See Fig. 3.) This insures that the ller will maintain itself in a vertical plane.

The filler 30 may be formed of any suitable material, but is preferably formed of paper or felt impregnated with asphalt or similar material.

If desired, a temporary ller in the form of a metal plate, may be introduced and removed later.

In addition to the cover plate i6, I may provide one or more follower plates 35 and 3S. These follower plates are connected to the cover plate it, and to each other, by flexible joints 3l. These joints may be of any simple form, for example. they may consist of a U-shaped shackle 38, the arms of which are connected by a bolt 39 passing through adjacent upwardly projecting ianges e@ on transverseangle irons di, which are riveted to the upper side of the plates.

These follower plates 35 and 36 rest on the upper surface of the laid concrete, and form a smooth nished surface.

After the concrete strip 5 has been laid and before it has set, I impress it to form weakened planes d2. These planes of weakness are preferably located equidistant between the main joints d3 (see Fig. 2). In order to form these weakened planes or incipient joints, I prefer to provide a comb Elfi, which is in the form of a bar with a plurality of spurs d5 on its lower edge. These spurs 635 are preferably equidistant, and the under side of the bar is provided with a relatively thin` and shallow rib d. If desired, this comb may be operated by hand, but as it would require a considerable force to press the comb down into the concrete, I prefer to mount the comb on the apparatus (see Fig. 1) and provide for operating it by power. The comb is moved downwardly in a fixed plane and by a movement of translation, that is to say, without shifting it longitudinally. For this purpose, beyond the follower plate I mount a comb frame il at each side, connected to the rear edge of the plate 36 by a exible connection d8. This comb frame is supported on rollers or Wheels 39 that run on sills l. The comb extends transversely across the roadway, and at each end is provided with an actuating rod 50. Any suitable means may be provided for actuating these rods 5l! to force the comb down into the concrete. In the present instance, I have illustrated a compressed air cylinder 5i for this purpose. Means such as a spring 52 may be provided for normally holding the rod 50 in an elevated position. In the present instance, this spring is illustrated as mounted in the air cylinder below the piston 53. By admitting compressed air through a compressed air connection 5e, the

comb can .be driven down 'into lthe concrete with considerable force, thereby forming a plurality of pockets 55, which are disposed in a transverse row, and when these pockets are formed, the rib 46 will form a relatively shallow gutter 56 connecting these pockets.

After the concrete has set and hardened,v the gutter or channel 5t and the pockets 5E may bo filled with tar, asphalt or any other suitable composition, to seal the road surface.

Referring again to Figure 3, any suitable means may be employed for guiding and supporting the header plate ii. For example, the heads of the rods I5 may be guided in slots 58a respectively, and if desired, guide pins 5l may 15 'also be provided sliding through guide holes 53 in the member 9a.

The general operation of my apparatus and method will now be briefly described. The apparatus is advanced along the bed l by any suit- 20 able means such as a tractor, and as the hopper 2 is advanced, the .concrete gravitates down the inclined guide plate or bottom of the hopper, and is laid through the delivery opening onto the subgrade. As this takes place, the header 25? plate li is vibrated to condense the forward end of the concrete strip 5, and atthe same time, the cover plate i6 is vibrated in a vertical plane. This will condense the laid concrete. As the concrete passes down the outlet d, it is subjected 3e to vibration by the vibrating device on the ft From time to time, in order to form main joints in the laid concrete, the advance of the ap paratus isI arrested and the header plate ii is 35T withdrawn from the forward face of the laidV concrete so as to form the gap i@ for the intro duction of a joint ller 3d. (See Fig. 3.)

"When the hopper is arrested for this purpose and at other times, in order to formv the re- ,m mainder of the weakened planes, the comb i3d isl forced downwardly so as to impress the upper face of the laid concrete, thereby forming transverse rows of pockets et connectedby a shallow gutter ed to receive tar, asphalt, or other comw position.

With an apparatus of this kind, and in practicing my method, the concrete can be laid at a rapid rate, and by reason of the operation of the header plate ii and the vibrations employed, the m ordinary nd-tamping operations me un=` necessary.

After the concrete has set and rdened, if any transverse cracks tend to form in the concrete, they will ce fi. rr, form where the ver- @5 tical cross-section of the concrete is weakened by the planes of weess. In this way, cracks are induced at intermediate points between the regular joints, and such cracks will be hidden below the ller that is placed in the gutters t. w This, of course, avoids the tendency of the concrete to form into cracks visible on lthe upper face of the concrete, and produces a road that will wear well, and which will not have its appearance marred by surface cracks. If it were attempted to impress deeply the upper face of the laid concrete with a bar having a straight or regular lower edge, a transverse gutter or groove can be formed, but there is a tendency to form a raised ridge or burr on each side of 70 the gutter. Providing spurs such as the spurs d5, avoids this tendency, and the spurs guide the comb as it descends. The straight lower edge of the comb need not descend to much depth in the surface. The pockets .or holes formed by the spurs are the principal factor in' producing theweakened planes.

' If it is desired to form a central longitudinal dummy Joint in the laid pavement, this may be 5Y accomplished by-providing a bar 60 attached to the under side of the plate I8, and a similar bar 6| maybe secured under the follower plate 35 to'allgn with the bar 60. The bars 60 and 6| on these plates align to form a longitudinal channel 10 :62, in the pavement. Thischannel should, of

course, be filled with tar, asphalt, or other composition, and usually there would be one such channel formed in the center of the laid strip oi.' concrete.- This channel would have a depth of 15. fabout onesthrd the depth of the cross-section where it is located.

`A 'Iransverse reinforcing may be placed in the concrete, if desired, by laying transversely placed bars 63 into thehopper from time to time. These 0 :bars gravitate down with the concrete and form transverse reinforcing 64'. Longitudinal reinforcing can be placed by providing aligning openings 65 in the traction frame, and aligning openings 66 in the header plate Il, through which bars, .(indicated in dotted lines at'61 in Fig. 3) may be fed. This should be done, however, in such a way that the reinforcing bars will not extend across any of the regular joints where the fillers are placed. I 3 In using the 'term' vibration or vibrating means in this specification and claims, I mean rapid vibration at high frequency while maintaining contact with the concrete. This maintenance of contact distinguishes from tamping, in which contact is not maintained-and a blow is struck by an object having considerable mass.

As the vibrating'means for the cover plate is mounted on the hopper, it operates to vibrate the -hoppen which assists the downward movement of 40;the concrete, and condenses the concrete as it passes through the contracted throat at the outlet from the hopper.

The vibration imparted to the rear side of the hopper and to the cover plate I6, facilitates the passing of the bar 60 through the laid concrete so as to make a clean groove. This cooperation is eiected in two ways: rst. by reason of the fact that the vibration of the rear side of the hopper and the cover plate I8, tends to 0"bring the mortar to the surface ofthe laid concrete, which makes it easier for the'bar 60 to pass through, and leaves a smoother surface for the groove formed. Also, the vibratory' impulses imparted to the concrete while the bar 80 is being advanced, reduce the resistance of the larger portions of aggregate to the` passage of the bar. It is understood that the embodiment of the invention described herein, is only one of the many embodiments this invention may take, and '-`=I do not wish to be limited in the practice of the invention, nor in the claims, to the particular embodiment set forth.

What I claim is:- 1. In concrete laying apparatus, the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete is'discharged, means for advancing the hopper, an upright header plate located forward of the delivery opening with respect to the direct-ion-of advance of the hopper and maintained in contact'withjhe concrete as it is laid, and means locatedl at the header plate and attached tothe same for vibrating the header late. 'p 2. In concrete laying-apparatus. the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete is discharged, means for advancing the hopper, a cover plate connected with the hopper and located behind the delivery opening 5 with respect to the direction of advance of the hopper, a follower plate flexibly connected to the rear edge of the cover plate, said cover plate and said follower plate operating t9 lie on the laid concrete, a header plate located in a sub- L stantially vertical plane forward of the delivery opening with respect to the direction of advance of the hopper, withits side face constantly in contact with the concrete as it is laid, and means for imparting rapid vibratory movements to the l header plate and the cover plate.

3. In concrete laying apparatus, the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete is fed, means for advancing the hopper, 20

a header plate disposed in a substantially vertical `plane forwardly of the delivery opening with respect to the direction of advance of the hopper, and constantly in contact with concrete being laid, means for imparting rapid vibratory 23 movement to the header plate in a direction transverse to its plane, and means enabling the header plate to be held in a position withdrawn from the concrete to form a gap facilitating the introduction of a joint ller in the laid concrete. 30

4. In concrete laying apparatus, the combina- ,t tion of a hopper for holding a mass of concrete and having a, delivery opening through which the concrete is fed, means for advancing the hopper,

a header plate disposed in a substantially ver- 35 I .rality of spaced spurs on the under side thereof to be forced down into the upper face of the laid concrete. t

5. In concrete laying apparatus. the combina- 50 tion of a hopper for holding a mass of concrete and having a delivery opening through which the concrete is fed,.means for advancing the hopper, a comb with means for supporting the same connected so as to advance with the hopper, said 5,. comb extending transversely with respect to the' J direction of advance of the hopper and having a plurality of spaced spurs on its under side, and means for forcing the comb down onto the upper face of the laid concrete by a movement Bm of translation to impress the same, means for guiding said comb so as to hold the same against longitudinal shifting and so that the spurs move longitudinally on their own axes down into the' concrete, and operate to form a transverse row of relatively deep holes extending down into the laid concrete, said comb further having a longitudinal rib on its under side to impress a relatively shallow groove in the upper face of the laid concrete, to connect the holes. 70

6. In concrete laying apparatus, the combina. tion of a hopper for holding a mass oi' concrete and having a delivery opening through which the concrete is fed, means for advancing the hopper, tolay the concrete in a strip, a comb extendingl transversely with respect to the direction of ad- Vance of the hopper and normally supported in an elevated position above the laid concrete, said comb having means on its under face for impressing the upper face of the laid concrete, and means for holding said comb against shifting longitudinally and for guiding said comb to move down in a fixed plane by a movementl of translation, to impress depressions in the concrete.

'7. In concrete laying apparatus, the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete is fed, means for advancing the hopper,

a header plate disposed in a substantially vertical position forward of the effective delivery opening with respect to thedirection of advance of the hopper, so that the header plate is in contact with the concrete being laid, means for mounting the header plate to enable the same `to be withdrawn from the end of the concrete being laid to facilitate the insertion of a transverse joint ller, thereby enabling the concrete to be laid with transverse joints, and means for impressing the upper face of thelaid concrete between the said transversejoints.

8. In concrete laying apparatus, the combination of a hopper for the concrete and capable of being advanced to lay the concrete, an upright header plate against the forward end of the concrete being laid, movable means for supporting the header plate enabling the same to be withdrawn from the concrete being laid to form a gap adjacent the header plate to receive a ller, said hopper being capable of moving forward over the header plate thereafter to place concrete ahead of the filler.

9. In a concrete laying apparatus, for laying concrete on a subgrade, the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete is discharged directly onto the subgrade, means for advancing the hopper, and means for imparting vibrations to the rear Wall of the hopper at a point whose distance from the delivery opening is less than three times the width of the delivery opening.

10. In a concrete laying apparatus, the combination of a hopperfor holding a mass of concrete and having a delivery opening through which the concrete discharges, means for advancing the hopper, an upright header plate located forward of the .eective delivery opening with respect to the direction of advance of the hopper and with its side face maintained in contact with the concrete being laid, and means located on the forward side of the header plate with respect to the direction of advance of the hopper for imparting rapid Vibrations to the header plate.

11. In a concrete laying apparatus, the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete discharges, means for advancing the hopper, a header plate with its side face against the concrete being laid, said plate disposed in Va substantially vertical plane and located forward of the effective delivery opening with respect to the direction of advance of the hopper, and means located forward of the header -plate for imparting rapid vibratory motion to the same. g f i 12. In aconcrete'laying apparatus, the combination` of a hopper for holding a mass of concrete and having a delivery opening through which the concrete discharges, means for advancing the hopper, and a header plate extending transversely to the direction of advance, located forward of the effective delivery opening with its side face in a plane substantially perpendicular to the .finished surface of the concrete and against which 5 the concrete presses as it is laid from the hopper.

13. In concrete laying apparatus, the combination of a hopper for the concrete and capable of being advanced to lay the concrete, a header plate in a substantially vertical plane and resting constantly against the forward end of the concrete being laid, movable means for supporting the header plate enabling the same to be withdrawn in a forward direction to form a gap adjacent the header plate through which a ller may be inserted from above, said hopper being capable of moving forward over the header plate thereafter to place concrete ahead of the ller.

14. In concrete laying apparatus, the combination of means for laying the concrete in a strip, a u

plate maintained in contact with the forwardy endof the strip as it is laid, and vibrating means located on the forward side of the plate for imparting rapid vibrations to. the same.

15. A method of laying concrete, which consists in laying a strip of concrete and impressing rows of holes transversely in the concrete, said holes being spaced apart transversely of the strip and extending down to about half the depth of the concrete and thereby forming substantially weakened planes in the laid concrete.

16. In concrete laying apparatus, the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete discharges, means for advancing the y hopper to lay the concrete, a vibrator frame in advance of the hopper, a header plate carried thereby against the forward end of the laid concrete, said vibrator frame having a cover plate and being movable independently of the hopper to er1- able the hopper to be advanced over the vibrator frame to close the outlet from the hopper.

17. In concrete laying apparatus, the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete discharges, means for advancing the hopper to lay the concrete, a vibrator frame in advance of the hopper outlet, a header plate carried thereby for engaging the forward end of the placed concrete, saidvibrator frame having a cover plate below the level of the outlet, said vibrator frame being independently movable with respect to the hopper to enable the same to be withdrawn to place a joint ller against the end of the placed concrete and enabling the vibrator frame and the hopper to be advanced thereafter to lay the concrete forward of the joint filler.

18. A method of laying concrete, which consists in carrying concrete in a hopper having an outlet through which the concrete discharges, ad- 60 vancing the hopper to lay the concrete through the outlet, maintaining a header plate forward of the outlet in contact with the forward end of the placed concrete, at intervals withdrawing the header plate from the end of the placed concrete, 65 introducing a joint filler in a substantially vertical position between the header plate and the end of the placed concrete, advancing the hopper thereafter to bring the outlet forward of the joint ller to lay concrete forward of the same, 70 and returning the header plate thereafter to a position forward of the outlet. l l

19. A method of laying concretajwhich consists in carrying concrete in a hopper having an outlet through which the concrete is discharged, 75

advancing the hopper to lay the concrete through the outlet, maintaining a header plate to conne the concrete that is already laid forward of the outlet and so that the header plate is in contact with the forward end of the placed concrete, and vibrating the header plate as the hopper advances.

20. A method of laying concrete, which consists in carrying concrete in a hopper having an outlet throughwhich the concrete is discharged, advancing the hopper to lay the concrete through the outlet, maintaining a header plate to confine the concrete that is already laid forward of the outlet and so that the header plate is in contact with the forward end of the concrete that is already laid, vibrating the header plate as the hopper advances, and vibrating the hopper as the concrete discharges from the same.

21. In concrete laying apparatus, the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete is fed, means for advancing the hopper, and a comb extending transversely to the direction of advance of the hopper supported above, and out of contact with, the face of the laid concrete, said comb having a plurality of spurs spaced on the under side of the same and extending in a row transversely to the direction of advance of the hopper, and means for moving said comb downwardly in a fixed position so that said spurs pass down into the laid concrete, said spurs extending into the concrete to about half its depth, and thereby forming holes substantially weakening the concrete in a transverse line in which the holes extend and operating to locate cracks in the concrete at the transverse line.

22. In concrete laying apparatus, the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete is fed, means for advancing the hopper, and a comb extending transversely to the 'direction of advance of the hopper supported above the face of the laid concrete, said comb having a plurality of spaced spurs on the under side thereof, means for guiding the comb to move down in a vertical position so that the spurs advance in the laid concrete along their own axes and form holes passing down to about one-half the Vdepth of theconcrete and thereby forming a transverse weakened plane in the concrete in the plane of the said holes, said comb further having a rib on its under side of less width than the spurs for press,- ing a relatively shallow groove in the concrete between the holes formed by the spurs.

23. In concrete laying apparatus, the combination of a hopper for supporting a mass of concrete to be laid on a subgrade, said hopper having a bottom opening with a throat for the discharge of the concrete onto the subgrade. means for advancing the hopper and thereby causing the concrete to move down in an unbroken mass onto the subgrade, means for connning the concrete forwardly of the effective bottom opening with respect to its direction of advance, and thereby resisting pressure exerted by the weight of 'concrete lying in the bottom o ning, and means for subjecting the confined c ncrete to a rapid vibratory movement adjacent t e discharge opening for condensing the laid conc ete.

24. In concrete laying apparatus for laying concrete on a subgrade, the combination f a hopper for holding a mass of concrete, said hopper having an outlet through which the concrete is discharged continuously and directly upon the ltsub'grade, means for advancing the hopper to lay. the concrete on the subgrade, and means located below 'tion of movable means for continuously placing the concrete i'n a strip and vibrating means for imparting rapid vibratory impulses mounted to advance with the first-named means and malntained in contact with the forward end face of the concrete already placed and at rest in the strip while the concrete is being placed in the strip.

27. In a concrete laying apparatus, for laying concrete on a. subgrade, the combination of a hopper for holding a mass of concrete, said hopper having downwardly converging plates including a forward plate and a rear throat plate cooperatp ing to form a throat through which the concrete 25' is discharged directly onto the subgrade and so that it is conned between said plates, and means for imparting vibratory movement at a high fre quency to the throat plate to condense the concrete as it passes through the throat.

28. In concrete laying apparatus, the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete is discharged, means for advancing the hopper, a comb with means for supporting the same to the rear of the hopper so as to advance with the hopper, said comb extending transversely with respect to the direction of advance of the hopper and having a plurality of spurs spaced apart on its under side, means for guiding the comb to move downwardly in a fixed position while the hopper is at rest so that the spurs penetrate the laid concrete by moving along their own axes and thereby forming relatively deep pockets in the concrete, and thereby developing a plane of substantial weakness in the concrete extending transversely to the same at said pockets.

29. A method of laying concrete, which consists in laying a strip of concrete, forming transverse through joints in the concrete at intervals,

and impressing transverse rows of relatively deep pockets spaced transversely across the strip located at intermediate points between the through joints and extending down through the body of the laid concrete to a depth suiilcient to form transverse weakened planes. at which the cgne..

crete is substantially weakened, thereby caising Athe concrete strip when it cracks to crack a said weakened planes.

30. A method of laying concrete, which con--r sists in laying a strip of concrete and impressing transverse rows of relatively deep pockets spaced transversely across the strip and extending down through the. body of the laid concrete to about half the depth of the concrete, and thereby forming transverse weakened planes at which the concrete is substantially weakened, thereby ing with respect to the direction of advance of the hopper, a header plate located forward of the delivery opening with respect to the direction of advance of the hopper and having its side face constantly in contact with the forward end of concrete already laid and at rest on the subgrade, and means for imparting rapid vibratory movement to the header plate and the cover plate.

32. In concrete laying apparatus, the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete is discharged, means for advancing the hopper, a header plate located forward of the delivery opening with respect to the direction of advance of the hopper and constantly in contact with the concrete already laid and at rest on the subgrade, means for imparting rapid vibratory movement to the header plate in a direction transverse to its plane, and means enabling the header plate to be held in a position withdrawn from the concrete to form a gap facilitating the introductionof a joint ller in the laid concrete.

33. In concrete laying apparatus, the combination of a hopper for holding a mass of concrete and having a delivery opening through which the concrete is discharged, means for advancing the hopper, an upright header plate located forward of the delivery opening with respect to the direction of advance out of contact with the surface on which the concrete is being laid and maintained in Contact with the concrete as it is laid, and means for vibrating the header plate.

34. In concrete laying apparatus, the combination of a hopper for holding a mass of concrete comprising mortar and coarse aggregate, said hopper having a delivery opening through which the concrete is discharged, means for advancing the hopper, a cover plate connected with the hopper so as to advance therewith and operating to lie on the laid concrete, a rib extending below the cover plate in contact with the laid concrete, and means for vibrating the hopper at its delivery opening to impart vibrations to the concrete passing through the opening and to the concrete in contact with the rib, thereby facilitating the passage of the rib through the concrete.

35. In a concrete laying apparatus, -the combination of a frame, a hopper on the frame for supporting a concrete mixture including mortar and coarse aggregate, said hopper having front and rear walls forming an outlet throat through which the concrete passes, means for advancing the hopper to lay the concrete in a continuous strip, means for vibrating the hopper to condense the concrete as it passes through the throat, and operating to bring the mortar to Y the concrete in the hopper is supported on the subgrade, means for advancing the hopper and thereby causing the concrete to move down in its unbroken mass through the said opening onto the subgrade, and means located adjacent to the bottom opening for vibrating the mass of concrete while it is passing down, said bottom opening being maintained open while the vibratory impulses are occurring so that the weight 0f the mass of concrete in the hopper supported on the subgrade cooperates with the vibrating means to condense the laid concrete.

37. A method of forming weakened planes in a strip of concrete yet plastic, which consists in forming transverse rows of relatively deep pockets spaced apart transversely across the strip distances less than three times the thickness of the laid concrete and extending through the body of the laid concrete to an extent substantially greater than one-third the thickness of the laid concrete to form transverse weakened planes at which the concrete is substantially weakened, thereby causing the concrete strip when it cracks to crack the said weakened planes.

HOMER M. HADLEY. 

